Death
Death is the end of a living organism's life, technically defined in humans as either the permanent termination of heart function and respiration, or of brain activity. Afterlife While Death is understood in a purely physical sense, the nature of what lies beyond is that of a heavenly world. When a wizard or witch dies, unlike a Muggle, he or she an choose to stay behind as a ghost. Few opt to become ghosts, however, as it means they will never go on like all others do. If they choose to not become ghosts, they pass on into the new world of Heaven, as is understood in Christianity, and become angels. Those who cross over to Heaven cannot come back in any form resembling the physical body they had in life. Dark wizards do not go to heaven, but are simply thrust into a limbo state permanently after their death, not able to return as a ghost or pass into heaven. Immortality and Resurrection There is currently no way to magically reunite a person's soul with they body once they have died. The Resurrection Stone can recall someone who has died from the beyond, but they will return only in a semi-corporeal form, "less substantial" than a living body but "much more" than a ghost. However, while there exists no method of reversing death once it has occurred, there are certain things a witch or wizard can do to postpone their death or prolong their life. The Elixir of Life, which is made from the Philosopher's Stone, will grant a person extended life for as long as they continue to consume it. However, because the Philosopher's Stone was locked in a vault in 2001 to prevent this, this method is no longer available. Unicorn blood can keep alive a person who is near death, but unicorns are such pure, defenseless creatures that a person who kills one and drinks its blood will have "but a half-life." A witch or wizard who rips their soul through an act of murder can place that torn fragment inside of an external object called a Horcrux. By binding a part of their soul to the earth, the Horcrux prevents the wizard or witch from dying, even if their body is injured or completely destroyed. However, there is a cost to using Horcruxes, a person's physical and mental conditions deteriorate after creating one. There is a potion which enables the Horcrux-creator's body to be reconstructed in the case of a completely destroyed body. Corpses can also be reanimated through Dark magic. Known as Inferi, these creatures are not alive, and simply do whatever the wizard who controls them wants, like puppets. Study and Perception of Death There is a chamber in the Department of Mysteries where witches and wizards study the mysteries of death. In this chamber is the Veil, an ancient stone archway, which is a gateway between the world of the living and the world of the dead. People standing around the Veil may hear voices from the other side of those who have died. A person whose body passes through the Veil will die and pass into Heaven and cannot return. However, a Dark witch or wizard who attempts to pass through the Veil will rebound off and died and be trapped in a limbo state. Thestrals are magical creatures visible only to people who have witnessed a death firsthand. However, the ability to see thestrals does not come immediately, but only after one has had time to fully understand death and its finality.